3, -6, 12, 4, 20,...
The odd-numbered terms go:
3, 12, 20,
3+9=12
12+8=20
20+7=27, so continuing the pattern of adding 1 less each time:
27+6=33
33+5=38
3, 12, 20, 27, 33, 38,...
The even terms go
-6, 4,
-6+10 = 4
4+9 = 13 continuing the pattern of adding 1 less each time.
13+8 = 21
21+7 = 28
28+6 = 34
So the even-numbered terms go:
-6, 4, 13, 21, 34, ...
Put the odd-numbered terms and the even-numbered
terms together:
3, -6, 12, 4, 20, 13, 27, 21, 33, 34, 38,...
That's a pattern. It may not be the pattern your teacher had in
mind, but it's just as good as his. There are many possible
patterns for any sequence. It beats me how they can expect
you to come up the same pattern that they have in mind.
Edwin
